Method and apparatus for battery-backed power supply and battery charging

ABSTRACT

Apparatuses, systems, and methods for providing battery-backed power to movable partitions are disclosed. A power converter generates a DC output from an AC input. The DC output may be selectively decoupled from an enabled DC output such that the DC output can be monitored for acceptable operation in-situ. The enabled DC output may be selectively coupled to a battery output terminal. A charge current may be sensed between the enabled DC output and the battery output to control charging of the battery with a pulse-width modulation operation by controlling the selective coupling of the enabled DC output to the battery output. The enabled DC output and the battery output are coupled in a logical-or configuration to generate a supply output providing current from the enabled DC output and the battery. The supply output may drive a movable partition controller and a motor configured for opening and closing a movable partition.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.11/699,729, filed Jan. 30, 2007, pending, the disclosure of which ishereby incorporated herein by this reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to direct current power suppliesfor driving large current loads and more specifically to power suppliesincluding a battery backup that can be charged.

2. State of the Art

Automatic doors are implemented in various configurations such as, forexample, sliding doors, rotating panel doors, folding doors, andrevolving doors. Automatic doors are often relied on for security andfire safety purposes. For example, an automatic door system includingone or more accordion-type doors may be used as a security and/or a firedoor. These automatic doors are configured to open or closeautomatically dependent on a trigger such as a security or fireindicator. As a result, the automatic doors include control electronicsand one or more motors to control movement of the door. This motor andaccompanying control electronics must be driven by a power supply. Manyautomatic doors include a conventional power supply coupled to atraditional Alternating Current (AC) power source that converts the ACsupply to a Direct Current (DC) supply suitable for use by the motor andcontrol electronics.

However, in many emergency situations, a reliable AC power source maynot be available. To provide reliable power, many automatic doorsinclude a conventional AC/DC converter power supply coupled with abattery backup that switches in when the AC power source is compromised.Furthermore, in some cases, the power source for the automatic door mayinclude a battery charger for maintaining the battery at a full chargevia AC/DC converter power supply.

A need exists to provide a more reliable and efficient power source thatcan provide power from a conventional AC source as well as a batterybackup to provide power for a motor and accompanying control electronicsof an automatic door.

BRIEF SUMMARY OF THE INVENTION

The present invention provides apparatuses and methods for providingbattery charging and contemporaneous battery-backed power useful incontrolling and motivating automatic doors. The present invention alsoprovides apparatuses and methods for providing efficient in-situcharging of the battery as well as efficient in-situ testing of an AC/DCpower converter.

An embodiment of the present invention is a method of providingbattery-backed power. The method includes providing a power converterfor generating a DC output from an AC input. The DC output may beselectively decoupled from an enabled DC output such that the DC outputcan be monitored for acceptable operation in-situ. The enabled DC outputmay be selectively coupled to a battery output terminal of a battery.The method also includes sensing a charge current between the enabled DCoutput and the battery output to control charging of the battery with apulse-width modulation operation by controlling the selective couplingof the enabled DC output to the battery output. The enabled DC outputand the battery output are coupled in a logical-or configuration togenerate a supply output that provides current from the enabled DCoutput when it is enabled as well as from the battery.

In another embodiment of the present invention, a battery-backed powersupply includes a power converter with an AC input and a DC output. Afirst diode is operably coupled in a forward biased configurationbetween the DC output and a biased DC output. A supply switch isconfigured for selectively coupling the biased DC output to a supplyoutput such that the DC output can be monitored for acceptable powerconverter operation in-situ. A battery switch is configured forselectively coupling the supply output to a battery-charge signal and abattery is operably coupled between a ground and a battery output. Acurrent sensor is operably coupled in series between the battery-chargesignal and the battery output. A second diode is operably coupledbetween the battery output and the supply output. A controller isconfigured for charging the battery by controlling the battery switchwith a pulse-width modulation operation and configured for controllingthe supply switch to cause the selective coupling between the biased DCoutput and the supply output.

In another embodiment of the present invention, a movable partitionsystem includes the battery-backed power supply and a movable partitioncontroller operably coupled to the supply output and including a motorconfigured for opening and closing a movable partition. The movablepartition system may include additional components depending, forexample, on the intended application of the motor. For example, in oneembodiment the motor may be operably coupled to a portion of a movablepartition in order to deploy and retract or otherwise displace thepartition. Such a partition may include, for example, a folding oraccordion-style door having a plurality of hingedly coupled panels. Thepartition may be configured as a fire barrier in one particular example.Of course, the system may include other components and be configured forother applications as will be appreciated by those of ordinary skill inthe art.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, which illustrate embodiments of the invention:

FIG. 1 is an elevation view of a movable partition in accordance withone embodiment of the present invention;

FIG. 2 is a plan view of the movable partition shown in FIG. 1;

FIG. 3 is a perspective view of a movable partition shown in FIGS. 1 and2;

FIG. 4 is a block diagram of battery-backed power supply according to anembodiment of the present invention;

FIG. 5 is a flow diagram illustrating a pulse-width modulation operationfor charging a battery according to an embodiment of the presentinvention; and

FIG. 6 is a flow diagram illustrating an example of an overall flow foroperating various aspects of the battery-backed power supply accordingto an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides apparatuses and methods for providingbattery charging and contemporaneous battery-backed power useful incontrolling and motivating automatic doors. The present invention alsoprovides apparatuses and methods for providing efficient in-situcharging of the battery as well as efficient in-situ testing of an AC/DCpower converter.

In the following description, circuits and functions may be shown inblock diagram form in order not to obscure the present invention inunnecessary detail. Conversely, specific circuit implementations shownand described are only examples and should not be construed as the onlyway to implement the present invention unless specified otherwiseherein. For the most part, details concerning timing considerations andthe like have been omitted inasmuch as such details are not necessary toobtain a complete understanding of the present invention and are withinthe ability of persons of ordinary skill in the relevant art.

Some drawings may illustrate signals as a single signal for clarity ofpresentation and description. It will be understood by a person ofordinary skill in the art that the signal may represent a bus ofsignals, wherein the bus may have a variety of bit widths and thepresent invention may be implemented on any number of data signalsincluding a single data signal.

Referring to FIGS. 1 through 3, an elevation view, a plan view and aperspective view are shown, respectively, of a moveable partition 100.It is noted that, in FIG. 3, various portions of certain structures orcomponents are partially sectioned for sake of clarity and simplicity inshowing various aspects of the described embodiment. In the exampleshown in FIGS. 1 through 3, the moveable partition 100 may be in theform of folding door. In certain embodiments, the partition 100 may beused, for example, as a security door, a fire door or as both. In otherembodiments, the partition need not be utilized as a fire or securitydoor, but may be used simply for the subdividing of a larger space intosmaller rooms or areas.

The partition 100 may be formed with a plurality of panels 102 that areconnected to one another with hinges or other hinge-like structures 104in an alternating pattern of panels 102 and hinge structures 104. Thehinged connection of the individual panels 102 enables the panels tofold relative to each other in an accordion or a plicated manner suchthat the partition 100 may be compactly stored, such as in a pocket 106formed in a first wall 108A of a building when the partition is in aretracted or folded state.

When in a deployed state, the partition 100 may extend from the firstwall 108A to a second wall 108B to act as a barrier (e.g., a fire orsecurity barrier) or to divide one area or room into multiple rooms 110Aand 110B. When it is desired to deploy the partition 100 from a stowedcondition to an extended position, for example to secure an area duringa fire, the partition 100 may be motivated along an overhead track 112(see FIG. 3) across the space to provide an appropriate barrier. When ina deployed or an extended state, a leading edge of the partition 100,shown as a male lead post 114, may complementarily or matingly engagewith a jamb or door post 116 that may be formed in the second wall 108Bof a building.

As best seen in FIG. 2, the partition 100 may include a first barrier orstructure 118A and a second barrier or structure 118B, each including aplurality of panels 102 coupled with one another by way of hinges orhinge-like structures 104. The second structure 118B is laterally spacedfrom the first structure 118A. Such a configuration may be utilized as afire door wherein one structure (e.g., structure 118A) acts as a primaryfire and smoke barrier, the space 120 between the two structures 118Aand 118B acts as an insulator or a buffer zone, and the anotherstructure (e.g., structure 118B) acts as a secondary fire and smokebarrier. Such a configuration may also be useful in providing anacoustical barrier when the partition is used to subdivide a largerspace into multiple, smaller rooms.

Various means may be used to displace the partition 100 from a stowedcondition to a deployed condition and vice versa. In one embodiment, anappropriate actuator may be used to displace the partition 100. Forexample, a drive may include a motor 122 coupled to a pulley or gear 123configured to drive a transmission member such as a belt or chain 124.

A portion of the belt or chain 124 may be coupled to a trolley 125 thatis configured to ride along the track 112. The trolley 125 may becoupled to a component of the partition 100 such as, for example, thelead post 114. Thus, actuation of the motor 122 and belt or chain 124 ina first direction results in displacement of the trolley 125 and leadpost 114 so that the partition may be deployed. Actuation of the motor122 and belt or chain 124 in a second direction results in displacementof the trolley 125 and lead post 114 so that the partition may beretracted.

Additionally, various sensors, switches, and control electronics may beemployed in association with such a drive to assist in the control ofthe partition 100. These electronic components may be generally andcollectively referred to as a movable partition controller 140. Whileshown as a box on the first wall 108A, those of ordinary skill in theart will recognize that the sensors, switches and other electroniccomponents may be distributed at various locations in and around themovable partition 100. As an example of control electronics, as shown inFIG. 1 and when used as a fire door, the partition 100 may include aswitch or actuator 128, commonly referred to as “panic hardware.”Actuation of the actuator 128 allows a person located on one side of thepartition 100 (e.g., in room 110A) to cause the partition 100 to open ifit is closed, or to stop while it is closing, so as to provide accessthrough the barrier formed by the partition 100 for a predeterminedamount of time.

It is noted that, while the above description has been more directed toan embodiment including a single partition 100 extending from the firstwall 108A to the second wall 108B, other movable partitions may beutilized. For example, a two-door, or bi-part partition configurationmay be utilized wherein two similarly configured partitions extendacross a space and join together to form an appropriate barrier as willbe appreciated by those of ordinary skill in the art.

The motor 122 and movable partition controller 140 need electric powerto operate. This electrical power is provided by a power supply, whichmay be placed locally, for example, perhaps at a location within thepocket 106. Alternatively, the power supply may be placed remotely fromthe movable partition 100 with power lines running from a battery-backedpower supply to the motor 122 and movable partition controller 140.

FIG. 4 is a block diagram of a battery-backed power supply 200 accordingto an embodiment of the present invention. The battery-backed powersupply 200 includes a power converter 210 with an alternating current(AC) input 205 and a direct current (DC) output 212. A battery 260 isincluded and connected between a ground and a battery output 264. Thebattery is configured for supplying current to a supply output 296 whenthe power converter 210 is removed, un-operational, or fails to supply asufficient voltage level.

The power converter 210 may be any suitable AC to DC power supply, suchas, for example, a conventional switching power supply. The AC input 205may generally be a conventional 60 Hz nominal 115-volt AC power signal.As examples only, and not limitations, the DC output 212 may be arelatively high current output with a voltage such as about 15 volts orabout 28 volts suitable for providing power to a 12-volt or 24-volt DCmotor in the movable partition system.

The battery 260 may be any battery suitable for delivering a relativelyhigh current suitable for driving the motor 122 of the movable partitionsystem. By way of example, and not limitation, suitable batteries mayinclude lead-acid batteries and valve regulated lead acid batteries suchas gel-cell batteries and absorbent glass mat batteries. Of course,while represented as a single battery, those of ordinary skill in theart will recognize that the battery 260 may be configured as multiplebatteries coupled in series, parallel, or combinations thereof, togenerate the appropriate voltage and current levels.

A first diode D1 is connected to the DC output 212 in a forward biaseddirection between the DC output 212 and a biased DC output 214.Similarly, a second diode D2 is connected to the battery output 264 in aforward biased direction between the battery output 264 and a biasedbattery output 266. A supply switch S1 is connected in series betweenthe biased DC output 214 and an enabled DC output 216. As a result, whenthe supply switch S1 is closed, the biased DC output 214 and the biasedbattery output 266 are coupled together to drive the supply output 296in a logical-or configuration. Unlike many conventional battery-backedpower supplies, this configuration eliminates the need for a transferswitch for selecting between a power supply output and a battery output.With the wired-or configuration, the diodes (D1 and D2) prevent reversebias current to the battery 260 or power converter 210 and enablecurrent to be delivered from a combination of the battery 260 and thepower converter 210. Of course, if the battery 260 is low on charge, thebattery voltage may be low so that most or all of the current to thesupply output 296 is provided by the power converter 210. Similarly, ifthe power converter is missing, supplying inadequate voltage, or thesupply switch S1 is open, most or all of the current to the supplyoutput 296 is provided by the battery 260. In addition, thisconfiguration creates a dual source from which to pull current in aheavy load condition.

The battery 260 may be charged through a combination of a controller 220sampling a current sensor 250 and controlling a battery switch S2. Thecurrent sensor 250 and the battery switch S2 are connected in seriesbetween the enabled DC output 216 and the battery output 264. When thebattery switch S2 is closed, a battery-charge signal 255 is generatedthat is of a suitable voltage and current level for charging the battery260. Operation of the battery charging process will be explained morefully below with respect to the discussion of FIG. 5.

The controller 220 may be any suitable processor, microcontroller, FieldProgrammable Gate Array (FPGA), or other suitable programmable deviceconfigured for controlling and sampling the various signal connectedthereto and generally controlling operation of the battery-backed powersupply 200 and the battery charging process. By way of example only, andnot limitation, a PIC 18F2220 microcontroller from MicroChip TechnologyInc. may be used. The controller 220 may be referred to herein as acontroller, processor, or microcontroller.

The current sensor 250 may be a Hall Effect current sensor, ammeter, orother current sensor suitable for generating an analog or digital signalwherein the signal is proportional to the amount of current flowingthrough the current sensor 250. In some embodiments, a Hall Effectcurrent sensor may be used to minimize or substantially eliminate anyvoltage drop that may occur across the current sensor 250. Currentsensors 250 configured to generate an analog signal may be coupled to ananalog-to-digital input of the microcontroller 220 to sample the inputand convert it to a digital value suitable for use by software on themicrocontroller 220. Current sensors 250 that generate a digital signalmay directly interface to a serial or parallel port on themicrocontroller 220 to present a digital value suitable for use bysoftware on the microcontroller 220.

A current limiter 257 may also be connected in this series path to limitthe amount of current flowing between the enabled DC output 216 and thebattery output. The current limiter 257 may be, for example, a positivetemperature coefficient (PTC) device. The PTC device operates such thatit heats up as the amount of current flowing through it increases. At apredefined temperature threshold, the impedance of the PTC deviceincreases to limit the amount of current flowing therethrough. When thePTC device cools, it returns to the lower impedance state allowing morecurrent to flow therethrough. Thus, the current limiter 257 can protectthe current sensor 250 from high currents as well as protecting thebattery from excessive current that may cause problems during thecharging process.

Embodiments of the present invention include mechanisms for determiningthe presence and operation of the power converter 210. An input monitor230 may be used for determining that an adequate AC input 205 is beingsupplied to the power converter 210. A supply monitor 240 may be used todetermine that an acceptable DC output 212 is being generated by thepower converter 210. In simple forms, the input monitor 230 and supplymonitor 240 may be configured as voltage dividers configured as a pairof resistors in series that generate an analog output voltageproportional to the input voltage. The voltage divider can reduce thevoltage of its input signal to a voltage that is appropriate forconnection to an-analog-to-digital converter input on themicrocontroller 220. Thus, the microcontroller 220 can periodicallysample an input voltage signal 232 from the input monitor 230 todetermine that an appropriate AC input 205 is being provided. Similarly,the microcontroller 220 can sample a supply voltage signal 242 from thesupply monitor 240 to determine that an acceptable DC output 212 isbeing generated. Operation of the DC output 212 detection is describedmore fully below in the discussion of FIG. 6. Of course, those ofordinary skill in the art will recognize that other voltage monitors maybe used for the input monitor 230 and supply monitor 240. By way ofexample, and not limitation, one or more of the monitors may beconfigured as an analog to digital converter that samples an analogsignal and presents the input voltage signal 232 and supply voltagesignal 242 as digital inputs representing a voltage level.

A battery monitor 270 is connected to the battery output 264 to monitorvoltage of the battery output 264. Similar to the input monitor 230 andsupply monitor 240, the battery monitor 270 may be a simple voltagedivider presenting a battery voltage signal 272 as an analog voltage tothe microcontroller 220. Alternatively, the battery monitor 270 may beanother suitable device for presenting to the microcontroller 220 thebattery voltage signal 272 as a parallel or serial digital signal thatis proportional to the voltage of the battery output 264.

The battery-backed power supply 200 may also include a temperaturesensor 280, a fan 290, and a notification element 292. The temperaturesensor 280 may be positioned substantially near the power converter 210to monitor temperature of the power converter 210. Thus, as is explainedmore fully below during the discussion of FIG. 6, the microcontroller220 may control operation of the fan 290, or cause other suitable eventsto happen, if the temperature gets too high. The notification element292 may be operated by the microcontroller 220 to notify a user ofcertain events of interest that may occur during operation of thebattery-backed power supply 200. By way of example, and not limitation,the notification element 292 may be an element such as a speaker, alight emitting diode (LED), a liquid crystal display (LCD) or othersuitable element to notify a user of the status of the system.

Switches S1 and S2 are illustrated as simple controlled switches forease of description. By way of example, and not limitation, theseswitches may be implemented as bipolar transistors, field effecttransistors, relays, Micro Electro Mechanical System (MEMS) relays, orother suitable elements.

FIGS. 5 and 6 illustrate processes that may be carried out as computerexecutable instructions operating on the microcontroller 220. Unlessspecified otherwise, the order in which the processes are described isnot intended to be construed as a limitation. Furthermore, the processesmay be implemented in any suitable hardware, software, firmware, orcombinations thereof. By way of example, instructions for executing thesoftware processes may be stored on a storage device (not shown) andtransferred to memory (not shown) coupled to the controller 220, or maybe stored as firmware in a volatile or non-volatile fashion in memory onthe microcontroller 220.

When executed as firmware or software, the instructions for performingthe processes may be stored on a computer readable medium. A computerreadable medium includes, but is not limited to, magnetic and opticalstorage devices such as disk drives, magnetic tape, CDs (compact disks),DVDs (digital versatile discs or digital video discs), and semiconductorelements such as RAM, DRAM, ROM, EPROM, and Flash memory.

FIG. 5 is a flow diagram illustrating a pulse-width modulation operationfor charging a battery according to an embodiment of the presentinvention. The battery charging uses intelligent control to achievefavorable charging conditions by monitoring the charge current that thebattery will accept and limiting the amount of time that the chargecurrent is applied to the battery. By using a pulse-width modulatedcurrent, the battery charging operation generates a charge current thatis as high as the battery will accept, but limits the average chargecurrent integrated over time to no higher than the recommended chargecurrent for the battery being charged.

In describing the battery charging operation 300, reference will be madeto both FIGS. 4 and 5. In general, element numbers on FIG. 4 are in theformat 2xx, while element numbers in FIG. 5 are in the format 3xx. Thebattery charging is achieved by setting the DC output 212 at a voltagesufficient to deliver a voltage to the battery output 264 that is atleast as high as the float charge voltage of the battery. The floatcharge voltage is generally a voltage that is high enough to sustain acharging current through the battery's internal resistance. Thus, the DCoutput 212 should be at a voltage sufficiently high when taking intoaccount voltage drops that may occur across the first diode D1, thesupply switch S1, the battery switch S2, the current sensor 250, and, ifpresent, the current limiter 257.

Furthermore, embodiments of the present invention use pulse widthmodulation (PWM) to charge the battery. With PWM the power converter 210can supply as much current as the battery 260 will accept for a portionof a charging period, then supply no current to the battery for thebalance of the charging period. As a result, the system may charge thebattery in a very efficient, but still safe, manner by determining theaverage current over the charging period and ensuring that the averagecurrent is substantially near the maximum recommended charge current forthe battery being charged.

The battery charging operation 300 may be implemented as a timed eventthat occurs on a periodic basis such as, for example, within a timedsoftware loop or at the occurrence of a timed event. To begin theoperation, process block 302 indicates that the battery voltage ismeasured, which is performed by the microcontroller 220 reading thebattery voltage signal 272 generated by the battery monitor's 270representation of the voltage of the battery output 264.

Decision block 304 tests to see if the battery 260 needs charging. Thistest includes determining if the voltage of the battery output 264 islower than the float charge voltage of the battery to be charged. Ifnot, control passes down to decision block 316.

If the battery needs charging, operation block 306 enables the chargecurrent, which is done by controlling a signal to close the batteryswitch S2. At a small time delay after the charge current is enabled,operation block 308 measures the charge current. The charge current ismeasured by the controller 220 sampling a signal from the current sensor250, which gives an indication of the magnitude of current that thebattery 260 is accepting.

Operation block 310 calculates the charge pulse duty cycle that shouldbe applied to the battery. In other words, a cycle time for a chargingperiod is determined. By way of example, and not limitation, thischarging period may be defined as 6.6 milliseconds. Based on the batteryin the system, the battery will have a recommended maximum charge rate,which may be generally expressed in Amp-Hours. Generally, therecommended maximum charge rate is expressed as a percentage of therating of the battery, such as, for example, 0.2*C, where C is thebattery rating in Amp-Hours. Thus, if the battery is rated for 18Amp-Hours, the average charge rate should be held near or below 3.6Amp-Hours. By using pulse width modulation, a large current is appliedfor a portion of the charging period and no current is applied for thebalance of the charging period such that the time averaged current isnear or below the maximum charge current rating of the battery.

With the charge pulse-width duty cycle determined, a charge pulseduration is determined and decision block 312 waits for the charge pulseduration to expire. This duration may be implemented, for example, as asoftware loop or a timer.

When the charge pulse duration is complete, operation block 314 disablesthe charge current, which is done by controlling a signal to open thebattery switch S2.

Decision block 316 tests to see if a battery is actually present in thesystem, which is accomplished by the controller 220 sampling the batteryvoltage signal 272 which should indicate a voltage of substantially nearzero when there is no battery present. If there is no battery present,operation block 318 sets a flag indicating that a battery is missing.This flag may be used by other software routines operating on themicrocontroller. Of course, the operation of testing for a batterypresent may be performed before or after the charging operations.Furthermore, those of ordinary skill in the art will recognize that theoperations may be configured such that the charging operation includingblocks 306, 308, 310, 312 and 314, may be performed when the battery ispresent or when the battery is not present.

Decision block 320 indicates a loop that waits for the duration of thecharge period (i.e., the portion of the charge period when the chargecurrent is off) to complete. The operation of the loop shown by decisionblock 320 may be accomplished in multiple ways. As an example, if themicrocontroller 220 is operating on a global timing loop thatapproximates the charge period, decision block 320 would wait for a timeperiod that is approximately the global loop time, less the charge pulseduration time, less the time to execute other operations within theglobal loop. On the other hand, if the battery charging operation 300 isconfigured to execute at a regularly scheduled interval (i.e., thecharge period), decision block 320 is not needed and the batterycharging operation 300 would simply exit, since it would be executedagain at the next regularly scheduled interval.

FIG. 6 illustrates a global loop that may be used for operating variousaspects of the battery-backed power supply 200. In describing the globalloop 400, reference will be made to both FIGS. 4 and 6. In general,element numbers on FIG. 4 are in the format 2xx, while element numbersin FIG. 6 are in the format 4xx. The global loop begins with the batterycharging operation 300, the details of which are illustrated in FIG. 5.As already stated, if the global loop includes a specific timing loopthe battery charge routine would be executed once for each time throughthe loop. It is not necessarily important where within the loop thebattery charge routine is executed. If, on the other hand, the batterycharge routine is executed based on a periodic timer, it would executewhen the periodic timer expires (e.g., as an interrupt routine) atwhatever point the global loop is at when the timer expires.

Operation block 404 indicates other operations that may be performed aspart of the global loop. These operations need not be described hereinbecause they are not relevant to aspects of the present invention.Furthermore, it is not necessarily important where these operationsoccur within the global loop.

Decision block 406 tests the missing battery flag that may have been setin the battery charging routine. If the missing battery flag is set,operation continues at operation block 424. If the missing battery flagis not set, decision block 412 tests to see if an AC voltage is present.This action is performed by the microcontroller 220 reading the inputvoltage signal 232 generated by the input monitor's 230 representationof the voltage of the AC input 205. If there is no AC voltage present,control transfers to operation block 420.

If AC voltage is present, operation block 414 disconnects the powersupply, which is accomplished by the microcontroller 220 controlling asignal to open the supply switch S1. With the supply switch S1 open, theoutput voltage can be properly tested with no other circuitryintervening and possibly modifying the state of the DC output 212.

Operation block 416 measures the power supply, which is accomplished bythe microcontroller 220 reading the supply voltage signal 242 generatedby the supply monitor's 240 representation of the voltage of the DCoutput 212.

Decision block 418 tests to see if the power supply is functioningproperly, which could be, for example, a test to see that the sampledsupply voltage signal 242 is within predetermined boundaries for thesettings and type of power converter 210 in use. If the power supply isnot functioning properly, operation block 420 sets one or more powersupply problem flags. For example, these flags may indicate lack of ACinput 205, lack of DC output 212, or combination thereof. If the powersupply is functioning properly, operation block 422 reconnects the powersupply by the microcontroller 220 controlling a signal to close thesupply switch S1.

Operation block 424 measures the temperature within the power supply bythe microcontroller 220 sampling a signal from the temperature sensor280. Based on decision block 426, if the temperature is too high,operation block 428 turns the fan on. If the temperature is not toohigh, operation block 430 turns the fan off. This operation of thetemperature sensing may include some hysteresis. In other words, turningthe fan on may occur when the temperature exceeds a first temperaturethreshold, while turning the fan off may occur when the temperaturefalls below a second temperature threshold.

After controlling the fan through operation block 428 or 430, the globalloop returns to the battery charging operation 300 and repeats.

Although the present invention has been described with reference toparticular embodiments, the present invention is not limited to thesedescribed embodiments. Rather, the present invention is limited only bythe appended claims, which include within their scope equivalent devicesand methods that operate according to the principles of the presentinvention as described.

1. A movable partition system, comprising: at least one movablepartition; a battery-backed power supply, comprising: a power converterwith an alternating current (AC) input and a direct current (DC) output;a first diode operably coupled in a forward biased configuration betweenthe DC output and a biased DC output; a supply switch configured forselectively coupling the biased DC output to a supply output; a batteryoperably coupled between a ground and a battery output; a battery switchconfigured for selectively coupling the supply output to abattery-charge signal; a current sensor operably coupled in seriesbetween the battery-charge signal and the battery output; a second diodeoperably coupled between the battery output and the supply output; and acontroller configured for charging the battery by controlling thebattery switch with a pulse-width modulation operation and configuredfor controlling the supply switch to cause the selective couplingbetween the biased DC output and the supply output; and a movablepartition controller operably coupled to the supply output and includinga motor configured for displacing the at least one movable partition. 2.The movable partition system of claim 1, further comprising: atemperature sensor operably coupled to the controller; a fan operablycoupled to the controller; and wherein the controller is furtherconfigured to sample a signal from the temperature sensor correspondingto a temperature at a location substantially near the power converter,enable the fan if the sampled signal is above a predeterminedtemperature threshold, and disable the fan if the sampled signal isbelow the predetermined temperature threshold.
 3. The movable partitionsystem of claim 1, further comprising: a supply monitor operably coupledbetween the DC output and the controller and configured to generate asupply voltage signal corresponding to a voltage of the DC output; andwherein the controller is further configured for decoupling the biasedDC output and the supply output, sampling the supply voltage signalafter the decoupling, and coupling the biased DC output and the supplyoutput after the sampling.
 4. The movable partition system of claim 3,further comprising: an input monitor operably coupled between the ACinput and the controller and configured to generate an input voltagesignal corresponding to a voltage of the AC input; and wherein thecontroller is further configured to bypass the operations of decoupling,sampling, and coupling if the input voltage signal indicates that the ACinput is inactive.
 5. The movable partition system of claim 1, furthercomprising: a battery monitor operably coupled between the batteryoutput and the controller and configured to generate a battery voltagesignal corresponding to a voltage at the battery output; and wherein thecontroller is further configured to sample the battery voltage signaland enable the pulse-width modulation operation if the battery voltagesignal is below a predetermined battery threshold.
 6. The movablepartition system of claim 20, wherein the controller is furtherconfigured to control the pulse-width modulation operation by: operatingthe battery switch to couple the supply output to the battery output;sensing a charge current from the current sensor; calculating acharge-pulse duration correlated to the charge current; operating thebattery switch to decouple the supply output from the battery outputafter the charge-pulse duration; waiting for a charge-cycle duration tocomplete; and repeating the operations of operating the battery switchto couple, sensing, calculating, operating the battery switch todecouple, and waiting.
 7. The movable partition system of claim 1,wherein the supply switch and the battery switch each comprise anelement selected from the group consisting of a field effect transistor,a bipolar transistor, a relay, or a MEMS relay.
 8. The movable partitionsystem of claim 1, wherein the current sensor comprises an elementselected from the group consisting of a Hall Effect current sensor andan ammeter.
 9. The movable partition system of claim 1, wherein thebattery is selected from the group consisting of a lead-acid battery, avalve regulated lead-acid battery, a gel-cell battery, and an absorbentglass mat battery.